draft-ietf-mpls-tp-gach-gal-06.txt   rfc5586.txt 
MPLS Working Group M. Bocci, Ed. Network Working Group M. Bocci, Ed.
Internet-Draft M. Vigoureux, Ed. Request for Comments: 5586 M. Vigoureux, Ed.
Updates: 3032, 4385, 5085 Alcatel-Lucent Updates: 3032, 4385, 5085 Alcatel-Lucent
(if approved) S. Bryant Category: Standards Track S. Bryant, Ed.
Intended status: Standards Track Cisco Cisco Systems
Expires: November 22, 2009
May 21, 2009
MPLS Generic Associated Channel MPLS Generic Associated Channel
draft-ietf-mpls-tp-gach-gal-06
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Status of This Memo
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on November 22, 2009. This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info). publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
skipping to change at page 2, line 39 skipping to change at page 2, line 28
4. Generalized Exception Mechanism . . . . . . . . . . . . . . . 9 4. Generalized Exception Mechanism . . . . . . . . . . . . . . . 9
4.1. Relationship with Existing MPLS OAM Alert Mechanisms . . . 9 4.1. Relationship with Existing MPLS OAM Alert Mechanisms . . . 9
4.2. GAL Applicability and Usage . . . . . . . . . . . . . . . 10 4.2. GAL Applicability and Usage . . . . . . . . . . . . . . . 10
4.2.1. GAL Processing . . . . . . . . . . . . . . . . . . . . 10 4.2.1. GAL Processing . . . . . . . . . . . . . . . . . . . . 10
4.3. Relationship with RFC 3429 . . . . . . . . . . . . . . . . 13 4.3. Relationship with RFC 3429 . . . . . . . . . . . . . . . . 13
5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 14 5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 14
6. Congestion Considerations . . . . . . . . . . . . . . . . . . 15 6. Congestion Considerations . . . . . . . . . . . . . . . . . . 15
7. Major Contributing Authors . . . . . . . . . . . . . . . . . . 15 7. Major Contributing Authors . . . . . . . . . . . . . . . . . . 15
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
9. Security Considerations . . . . . . . . . . . . . . . . . . . 15 9. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . . 17 11.1. Normative References . . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . . 18 11.2. Informative References . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
There is a need for Operations, Administration and Maintenance (OAM) There is a need for Operations, Administration, and Maintenance (OAM)
mechanisms that can be used for fault detection, diagnostics, mechanisms that can be used for fault detection, diagnostics,
maintenance and other functions on a pseudowire (PW) and a Label maintenance, and other functions on a pseudowire (PW) and a Label
Switched Path (LSP). These functions can be used between any two Switched Path (LSP). These functions can be used between any two
Label Edge Routers (LERs) / Label Switching Router (LSRs) or Label Edge Routers (LERs) / Label Switching Router (LSRs) or
Terminating Provider Edge routers (T-PEs) / Switching Provider Edge Terminating Provider Edge routers (T-PEs) / Switching Provider Edge
routers (S-PEs) along the path of an LSP or PW respectively [11]. routers (S-PEs) along the path of an LSP or PW, respectively
Some of these functions can be supported using existing tools such as [MPLS-TP]. Some of these functions can be supported using existing
Virtual Circuit Connectivity Verification (VCCV) [1], Bidirectional tools such as Virtual Circuit Connectivity Verification (VCCV)
Forwarding Detection for MPLS LSPs (BFD-MPLS) [12], LSP-Ping [13], or [RFC5085], Bidirectional Forwarding Detection for MPLS LSPs (BFD-
BFD-VCCV [14]. However, a requirement has been indicated to augment MPLS) [BFD-MPLS], LSP-Ping [RFC4379], or BFD-VCCV [BFD-VCCV].
this set of maintenance functions, in particular when MPLS networks However, a requirement has been indicated to augment this set of
are used for packet transport services and transport network maintenance functions, in particular when MPLS networks are used for
operations [15]. Examples of these functions include performance packet transport services and transport network operations [OAM-REQ].
monitoring, automatic protection switching, and support for Examples of these functions include performance monitoring, automatic
management and signaling communication channels. These tools MUST be protection switching, and support for management and signaling
applicable to, and function in essentially the same manner (from an communication channels. These tools MUST be applicable to, and
operational point of view) on MPLS PWs, MPLS LSPs and MPLS Sections. function in essentially the same manner (from an operational point of
They MUST also operate in-band on the PW or LSP such that they do not view) on MPLS PWs, MPLS LSPs, and MPLS Sections. They MUST also
depend on Packet Switched Network (PSN) routing or on user traffic, operate in-band on the PW or LSP such that they do not depend on
and MUST also NOT depend on dynamic control plane functions. Packet Switched Network (PSN) routing or on user traffic, and MUST
NOT depend on dynamic control plane functions.
VCCV [1] can use an Associated Channel Header (ACH) to provide a PW VCCV [RFC5085] can use an Associated Channel Header (ACH) to provide
associated control channel between a PW's end points, over which OAM a PW associated control channel between a PW's endpoints, over which
and other control messages can be exchanged. This document OAM and other control messages can be exchanged. This document
generalizes the applicability of the ACH to enable the same generalizes the applicability of the ACH to enable the same
associated control channel mechanism to be used for Sections, LSPs associated control channel mechanism to be used for Sections, LSPs,
and PWs. The associated control channel thus generalized is known as and PWs. The associated control channel thus generalized is known as
the Generic Associated Channel (G-ACh). The ACH, specified in RFC the Generic Associated Channel (G-ACh). The ACH, specified in RFC
4385 [2], may be used with additional code points to support 4385 [RFC4385], may be used with additional code points to support
additional MPLS maintenance functions on the G-ACh. additional MPLS maintenance functions on the G-ACh.
Generalizing the applicability of the ACH to LSPs and Sections also Generalizing the applicability of the ACH to LSPs and Sections also
requires a method to identify that a packet contains an ACH followed requires a method to identify that a packet contains an ACH followed
by a non-service payload. Therefore, this document also defines a by a non-service payload. Therefore, this document also defines a
label based exception mechanism that serves to inform an LSR (or LER) label-based exception mechanism that serves to inform an LSR (or LER)
that a packet it receives on an LSP or Section belongs to an that a packet it receives on an LSP or Section belongs to an
associated control channel. The label used for that purpose is one associated control channel. The label used for that purpose is one
of the MPLS reserved labels and is referred to as the GAL (G-ACh of the MPLS reserved labels and is referred to as the GAL (G-ACh
Label). The GAL mechanism is defined to work together with the ACH Label). The GAL mechanism is defined to work together with the ACH
for LSPs and MPLS Sections. for LSPs and MPLS Sections.
RFC 4379 [13] and BFD-MPLS [12] define alert mechanisms that enable RFC 4379 [RFC4379] and BFD-MPLS [BFD-MPLS] define alert mechanisms
an MPLS LSR to identify and process MPLS OAM packets when these are that enable an MPLS LSR to identify and process MPLS OAM packets when
encapsulated in an IP header. These alert mechanisms are based, for these are encapsulated in an IP header. These alert mechanisms are
example, on Time To Live (TTL) expiration and/or on the use of an IP based, for example, on Time To Live (TTL) expiration and/or on the
destination address in the range of 127.0.0.0/8 or 0:0:0:0:0:FFFF: use of an IP destination address in the range of 127.0.0.0/8 or 0:0:
127.0.0.0/104, respectively for IPv4 and IPv6. These mechanisms are 0:0:0:FFFF:127.0.0.0/104 for IPv4 and IPv6, respectively. These
the default mechanisms for identifying MPLS OAM packets when mechanisms are the default mechanisms for identifying MPLS OAM
encapsulated in an IP header. However it may not always be possible packets when encapsulated in an IP header. However, it may not
to use these mechanisms in some MPLS applications e.g., MPLS always be possible to use these mechanisms in some MPLS applications,
Transport Profile (MPLS-TP) [11], particularly when IP based e.g., MPLS Transport Profile (MPLS-TP) [MPLS-TP], particularly when
demultiplexing cannot be used. This document defines a mechanism IP-based demultiplexing cannot be used. This document defines a
that is RECOMMENDED for identifying and encapsulating MPLS OAM and mechanism that is RECOMMENDED for identifying and encapsulating MPLS
other maintenance messages when IP based mechanisms such as those OAM and other maintenance messages when IP based mechanisms such as
used in [13] and [12] are not available. Yet, this mechanism MAY be those used in [RFC4379] and [BFD-MPLS] are not available. Yet, this
used in addition to IP-based mechanisms. mechanism MAY be used in addition to IP-based mechanisms.
Note that, in this document, maintenance functions and packets should Note that, in this document, maintenance functions and packets should
be understood in the broad sense. That is, a set of maintenance and be understood in the broad sense. That is, a set of maintenance and
management mechanisms that include OAM, Automatic Protection management mechanisms that include OAM, Automatic Protection
Switching (APS), Signaling Communication Channel (SCC) and Management Switching (APS), Signaling Communication Channel (SCC), and
Communication Channel (MCC) messages. Management Communication Channel (MCC) messages.
Also note that the GAL and ACH are applicable to MPLS and PWs in Also note that the GAL and ACH are applicable to MPLS and PWs in
general. This document specifies general mechanism and uses MPLS-TP general. This document specifies general mechanism and uses MPLS-TP
as an example application. The application of the GAL and ACH to as an example application. The application of the GAL and ACH to
other specific MPLS uses is outside the scope of this document. other specific MPLS uses is outside the scope of this document.
1.1. Objectives 1.1. Objectives
This document defines a mechanism that provides a solution to the This document defines a mechanism that provides a solution to the
extended maintenance needs of emerging applications for MPLS. It extended maintenance needs of emerging applications for MPLS. It
creates a generic control channel mechanism that may be applied to creates a generic control channel mechanism that may be applied to
MPLS LSPs and Sections, while maintaining compatibility with the PW MPLS LSPs and Sections, while maintaining compatibility with the PW
associated channel. It also normalizes the use of the ACH for PWs in associated channel. It also normalizes the use of the ACH for PWs in
a transport context, and defines a label based exception mechanism to a transport context, and defines a label-based exception mechanism to
alert LERs/LSRs of the presence of an ACH after the bottom of the alert LERs/LSRs of the presence of an ACH after the bottom of the
label stack. label stack.
1.2. Scope 1.2. Scope
This document defines the encapsulation header for Sections, LSPs, This document defines the encapsulation header for Section, LSP, and
and PWs associated control channel messages. PW associated control channel messages.
It does not define how associated control channel capabilities are This document does not define how associated control channel
signaled or negotiated between LERs/LSRs or PEs, or the operation of capabilities are signaled or negotiated between LERs/LSRs or between
various OAM functions. PEs, nor does it define the operation of various OAM functions.
This document does not deprecate existing MPLS and PW OAM mechanisms. This document does not deprecate existing MPLS and PW OAM mechanisms.
1.3. Requirements Language and Terminology 1.3. Requirements Language and Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [3]. document are to be interpreted as described in RFC 2119 [RFC2119].
This document uses the following additional terminology: This document uses the following additional terminology:
ACH: Associated Channel Header ACH: Associated Channel Header
G-ACh: Generic Associated Channel G-ACh: Generic Associated Channel
GAL: G-ACh Label GAL: G-ACh Label
G-ACh packet: Any packet containing a message belonging to a protocol G-ACh packet: Any packet containing a message belonging to a protocol
that is carried on a PW, LSP or MPLS Section associated control that is carried on a PW, LSP, or MPLS Section associated control
channel. Examples include maintenance protocols such as OAM channel. Examples include maintenance protocols such as OAM
functions, signaling communications or management communications. functions, signaling communications, or management communications.
The terms 'Section' and 'Concatenated Segment' are defined in [16] as
follows (note that the terms 'Section' and 'Section Layer Network'
are synonymous):
Concatenated Segment: A serial-compound link connection as defined in The terms "Section" and "Concatenated Segment" are defined in
[17]. A concatenated segment is a contiguous part of an LSP or [TP-REQ] as follows (note that the terms "Section" and "Section Layer
multi-segment PW that comprises a set of segments and their Network" are synonymous):
interconnecting nodes in sequence.
Section Layer Network: A section layer is a server layer (which may Section Layer Network: A section layer is a server layer (which may
be MPLS-TP or a different technology) which provides for the transfer be MPLS-TP or a different technology) that provides for the transfer
of the section layer client information between adjacent nodes in the of the section layer client information between adjacent nodes in the
transport path layer or transport service layer. Note that G.805 transport path layer or transport service layer. Note that G.805
[17] defines the section layer as one of the two layer networks in a [G805] defines the section layer as one of the two layer networks in
transmission media layer network. The other layer network is the a transmission media layer network. The other layer network is the
physical media layer network. physical media layer network.
Concatenated Segment: A serial-compound link connection as defined in
[G805]. A concatenated segment is a contiguous part of an LSP or
multi-segment PW that comprises a set of segments and their
interconnecting nodes in sequence.
2. Generic Associated Channel Header 2. Generic Associated Channel Header
VCCV [1] defines three Control Channel (CC) Types that may be used to VCCV [RFC5085] defines three Control Channel (CC) Types that may be
exchange OAM messages through a PW: CC Type 1 uses an ACH and is used to exchange OAM messages through a PW. CC Type 1 uses an ACH
referred to as "In-band VCCV"; CC Type 2 uses the MPLS Router Alert and is referred to as "In-band VCCV"; CC Type 2 uses the MPLS Router
Label to indicate VCCV packets and is referred to as "Out of Band Alert Label to indicate VCCV packets and is referred to as "Out-of-
VCCV"; CC Type 3 uses the TTL to force the packet to be processed by Band VCCV"; CC Type 3 uses the TTL to force the packet to be
the targeted router control plane and is referred to as "MPLS PW processed by the targeted router control plane and is referred to as
Label with TTL == 1". "MPLS PW Label with TTL == 1".
2.1. Definition 2.1. Definition
The use of the ACH, previously limited to PWs, is here generalized to The use of the ACH, previously limited to PWs, is here generalized to
also apply to LSPs and to Sections. Note that for PWs, the PWE3 also apply to LSPs and to Sections. Note that for PWs, the PWE3
control word [2] MUST be present in the encapsulation of user packets control word [RFC4385] MUST be present in the encapsulation of user
when the ACH is used to realize the associated control channel. packets when the ACH is used to realize the associated control
channel.
The ACH used by CC Type 1 is depicted in figure below: The ACH used by CC Type 1 is depicted in figure below:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 1|Version| Reserved | Channel Type | |0 0 0 1|Version| Reserved | Channel Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Associated Channel Header Figure 1: Associated Channel Header
In the above figure, the first nibble is set to 0001b to indicate a In the above figure, the first nibble is set to 0001b to indicate a
control channel associated with a PW, an LSP or a Section. The control channel associated with a PW, LSP, or Section. The Version
Version field is set to 0, as specified in RFC 4385 [2]. Bits 8 to field is set to 0, as specified in RFC 4385 [RFC4385]. Bits 8 to 15
15 of the ACH are reserved and MUST be set to 0 and ignored on of the ACH are reserved and MUST be set to 0 and ignored on
reception. Bits 16 to 31 are used to encode the possible Channel reception. Bits 16 to 31 are used to encode the possible Channel
Types. This 16 bit field is in network byte order. Types. This 16-bit field is in network byte order.
Note that VCCV [1] also includes mechanisms for negotiating the Note that VCCV [RFC5085] also includes mechanisms for negotiating the
Control Channel and Connectivity Verification (i.e., OAM function) Control Channel and Connectivity Verification (i.e., OAM function)
Types between PEs. It is anticipated that similar mechanisms will be Types between PEs. It is anticipated that similar mechanisms will be
applied to LSPs. Such application will require further applied to LSPs. Such application will require further
specification. However, such specification is beyond the scope of specification. However, such specification is beyond the scope of
this document. this document.
The G-ACh MUST NOT be used to transport user traffic. The G-ACh MUST NOT be used to transport user traffic.
2.2. Allocation of Channel Types 2.2. Allocation of Channel Types
The Channel Type field indicates the type of message carried on the The Channel Type field indicates the type of message carried on the
associated control channel e.g., IPv4 or IPv6 if IP demultiplexing is associated control channel, e.g., IPv4 or IPv6 if IP demultiplexing
used for messages sent on the associated control channel, or OAM or is used for messages sent on the associated control channel, or OAM
other maintenance function if IP demultiplexing is not used. For or other maintenance function if IP demultiplexing is not used. For
associated control channel packets where IP is not used as the associated control channel packets where IP is not used as the
multiplexer, the Channel Type indicates the specific protocol carried multiplexer, the Channel Type indicates the specific protocol carried
in the associated control channel. in the associated control channel.
Values for the Channel Type field currently used for VCCV are Values for the Channel Type field currently used for VCCV are
specified elsewhere e.g., in RFC 4446 [4] and RFC 4385 [2]. specified elsewhere, e.g., in RFC 4446 [RFC4446] and RFC 4385
Additional Channel Type values and the associated maintenance [RFC4385]. Additional Channel Type values and the associated
functionality will be defined in other documents. Each document, maintenance functionality will be defined in other documents. Each
specifying a protocol solution relying on the ACH, MUST also specify document, specifying a protocol solution relying on the ACH, MUST
the applicable Channel Type field value. also specify the applicable Channel Type field value.
Note that these values are allocated from the PW Associated Channel Note that these values are allocated from the PW Associated Channel
Type registry [4], but this document modifies the existing policy to Type registry [RFC4446], but this document modifies the existing
accommodate a level of experimentation. See Section 10 for further policy to accommodate a level of experimentation. See Section 10 for
details. further details.
3. ACH TLVs 3. ACH TLVs
In some applications of the generalized associated control channel it In some applications of the generalized associated control channel,
is necessary to include one or more ACH TLVs to provide additional it is necessary to include one or more ACH TLVs to provide additional
context information to the G-ACh packet. One use of these ACH TLVs context information to the G-ACh packet. One use of these ACH TLVs
might be to identify the source and/or intended destination of the might be to identify the source and/or intended destination of the
associated channel message. However, the use of this construct is associated channel message. However, the use of this construct is
not limited to providing addressing information nor is the not limited to providing addressing information nor is the
applicability restricted to transport network applications. applicability restricted to transport network applications.
If the G-ACh message MAY be preceded by one or more ACH TLVs, then If the G-ACh message MAY be preceded by one or more ACH TLVs, then
this MUST be explicitly specified in the definition of an ACH Channel this MUST be explicitly specified in the definition of an ACH Channel
Type. If the ACH Channel Type definition does state that one or more Type. If the ACH Channel Type definition does state that one or more
ACH TLVs MAY precede the G-ACh message, an ACH TLV Header MUST follow ACH TLVs MAY precede the G-ACh message, an ACH TLV Header MUST follow
skipping to change at page 8, line 35 skipping to change at page 8, line 35
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Reserved | | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: ACH TLV Header Figure 3: ACH TLV Header
The Length field specifies the length in octets of the complete set The Length field specifies the length in octets of the complete set
of TLVs including sub-TLVs that follow the ACH TLV header. A length of TLVs including sub-TLVs that follow the ACH TLV Header. A length
of zero indicates that no ACH TLV follow this header. Note that no of zero indicates that no ACH TLV follow this header. Note that no
padding is required for the set of ACH TLVs. padding is required for the set of ACH TLVs.
The Reserved field is for future use and MUST be set to zero on The Reserved field is for future use and MUST be set to zero on
transmission and ignored on reception. transmission and ignored on reception.
3.3. ACH TLV Object 3.3. ACH TLV Object
ACH TLVs MAY follow an ACH TLV header. The structure of ACH TLVs is ACH TLVs MAY follow an ACH TLV Header. The structure of ACH TLVs is
defined and described in this section. defined and described in this section.
An ACH TLV consists of a 16-bit Type field, followed by a 16-bit An ACH TLV consists of a 16-bit Type field, followed by a 16-bit
Length field which specifies the number of octets of the Value field Length field that specifies the number of octets of the Value field,
which follows the Length field. This 32-bit word is followed by zero which follows the Length field. This 32-bit word is followed by zero
or more octets of Value information. The format and semantics of the or more octets of Value information. The format and semantics of the
Value information are defined by the TLV Type as recorded in the TLV Value information are defined by the TLV Type as recorded in the TLV
Type registry. See Section 10 for further details. Note that the Type registry. See Section 10 for further details. Note that the
Value field of ACH TLVs MAY contain sub-TLVs. Note that no padding Value field of ACH TLVs MAY contain sub-TLVs. Note that no padding
is required for individual TLVs or sub-TLVs. is required for individual TLVs or sub-TLVs.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 9, line 26 skipping to change at page 9, line 27
Figure 4: ACH TLV Format Figure 4: ACH TLV Format
4. Generalized Exception Mechanism 4. Generalized Exception Mechanism
Generalizing the associated control channel mechanism to LSPs and Generalizing the associated control channel mechanism to LSPs and
Sections also requires a method to identify that a packet contains an Sections also requires a method to identify that a packet contains an
ACH followed by a non-service payload. This document specifies that ACH followed by a non-service payload. This document specifies that
a label is used for that purpose and calls this special label the a label is used for that purpose and calls this special label the
G-ACh Label (GAL). One of the reserved label values defined in RFC G-ACh Label (GAL). One of the reserved label values defined in RFC
3032 [5] is assigned for this purpose. The value of the label is to 3032 [RFC3032] is assigned for this purpose. IANA assigned the value
be allocated by IANA. 13 to the GAL.
The GAL provides an alert based exception mechanism to: The GAL provides an alert based exception mechanism to:
o differentiate specific packets (i.e., G-ACh packets) from others, o differentiate specific packets (i.e., G-ACh packets) from others,
such as user-plane ones, such as user-plane ones.
o indicate that the ACH appears immediately after the bottom of the o indicate that the ACH appears immediately after the bottom of the
label stack. label stack.
The GAL MUST only be used where both these purposes apply. The GAL MUST only be used where both these purposes apply.
4.1. Relationship with Existing MPLS OAM Alert Mechanisms 4.1. Relationship with Existing MPLS OAM Alert Mechanisms
RFC 4379 [13] and BFD-MPLS [12] define alert mechanisms that enable RFC 4379 [RFC4379] and BFD-MPLS [BFD-MPLS] define alert mechanisms
an MPLS LSR to identify and process MPLS OAM packets when these are that enable an MPLS LSR to identify and process MPLS OAM packets when
encapsulated in an IP header. These alert mechanisms are based, for these are encapsulated in an IP header. These alert mechanisms are
example, on Time To Live (TTL) expiration and/or on the use of an IP based, for example, on Time To Live (TTL) expiration and/or on the
destination address in the range of 127.0.0.0/8 or 0:0:0:0:0:FFFF: use of an IP destination address in the range of 127.0.0.0/8 or 0:0:
127.0.0.0/104, respectively for IPv4 and IPv6. 0:0:0:FFFF:127.0.0.0/104 for IPv4 and IPv6, respectively.
These mechanisms are the default mechanisms for identifying MPLS OAM These mechanisms are the default mechanisms for identifying MPLS OAM
packets when encapsulated in an IP header although the mechanism packets when encapsulated in an IP header although the mechanism
defined in this document MAY also be used. defined in this document MAY also be used.
4.2. GAL Applicability and Usage 4.2. GAL Applicability and Usage
In MPLS-TP, the GAL MUST be used with packets on a G-ACh on LSPs, In MPLS-TP, the GAL MUST be used with packets on a G-ACh on LSPs,
Concatenated Segments of LSPs, and with Sections, and MUST NOT be Concatenated Segments of LSPs, and with Sections, and MUST NOT be
used with PWs. It MUST always be at the bottom of the label stack used with PWs. It MUST always be at the bottom of the label stack
(i.e., S bit set to 1). However, in other MPLS environments, this (i.e., S bit set to 1). However, in other MPLS environments, this
document places no restrictions on where the GAL may appear within document places no restrictions on where the GAL may appear within
the label stack or its use with PWs. Where the GAL is at the bottom the label stack or its use with PWs. Where the GAL is at the bottom
of the label stack (i.e., S bit set to 1) then it MUST always be of the label stack (i.e., S bit set to 1), then it MUST always be
followed by an ACH. followed by an ACH.
The GAL MUST NOT appear in the label stack when transporting normal The GAL MUST NOT appear in the label stack when transporting normal
user-plane packets. Furthermore, when present, the GAL MUST NOT user-plane packets. Furthermore, when present, the GAL MUST NOT
appear more than once in the label stack. appear more than once in the label stack.
A receiving LSR, LER or PE MUST NOT forward a G-ACh packet to another A receiving LSR, LER, or PE MUST NOT forward a G-ACh packet to
node based on the GAL label. another node based on the GAL label.
4.2.1. GAL Processing 4.2.1. GAL Processing
The Traffic Class (TC) field (formerly known as the EXP field) of the The Traffic Class (TC) field (formerly known as the EXP field) of the
Label Stack Entry (LSE) containing the GAL follows the definition and Label Stack Entry (LSE) containing the GAL follows the definition and
processing rules specified and referenced in [6]. processing rules specified and referenced in [RFC5462].
The Time-To-Live (TTL) field of the LSE that contains the GAL follows The Time-To-Live (TTL) field of the LSE that contains the GAL follows
the definition and processing rules specified in [7]. the definition and processing rules specified in [RFC3443].
4.2.1.1. MPLS Label Switched Paths and Segments 4.2.1.1. MPLS Label Switched Paths and Segments
The following figure (Figure 5) depicts two LERs (A and D) and two The following figure (Figure 5) depicts two LERs (A and D) and two
LSRs (B and C) for a given LSP which is established from A to D and LSRs (B and C) for a given LSP that is established from A to D and
switched in B and C. switched in B and C.
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
| A |-------------| B |-------------| C |-------------| D | | A |-------------| B |-------------| C |-------------| D |
+---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+
Figure 5: Maintenance over a LSP Figure 5: Maintenance over an LSP
In this example, a G-ACh exists on the LSP that extends between LERs In this example, a G-ACh exists on the LSP that extends between LERs
A and D, via LSRs B and C. Only A and D may initiate new G-ACh A and D, via LSRs B and C. Only A and D may initiate new G-ACh
packets. A, B, C and D may process and respond to G-ACh packets. packets. A, B, C, and D may process and respond to G-ACh packets.
The following figure (Figure 6) depicts the format of an MPLS-TP The following figure (Figure 6) depicts the format of an MPLS-TP
G-ACh packet when used for an LSP. G-ACh packet when used for an LSP.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP Label | TC |S| TTL | | LSP Label | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL | TC |S| TTL | | GAL | TC |S| TTL |
skipping to change at page 11, line 25 skipping to change at page 11, line 25
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~ | ~
~ Zero or more ACH TLVs ~ ~ Zero or more ACH TLVs ~
~ (if present) | ~ (if present) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~ | ~
~ G-ACh Message ~ ~ G-ACh Message ~
~ | ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: G-ACh packet format for a LSP Figure 6: G-ACh Packet Format for an LSP
Note that it is possible that the LSP may be tunneled in another LSP Note that it is possible that the LSP may be tunneled in another LSP
(e.g., if a MPLS Tunnel exists between B and C), and as such other (e.g., if an MPLS Tunnel exists between B and C), and as such other
LSEs may be present in the label stack. LSEs may be present in the label stack.
To send a G-ACh message on the LSP associated control channel, the To send a G-ACh message on the LSP associated control channel, the
LER (A) generates a G-ACh message, to which it MAY prepend an ACH TLV LER (A) generates a G-ACh message, to which it MAY prepend an ACH TLV
Header and appropriate ACH TLVs. It then adds an ACH, onto which it Header and appropriate ACH TLVs. It then adds an ACH, onto which it
pushes a GAL LSE. Finally, the LSP Label LSE is pushed onto the pushes a GAL LSE. Finally, the LSP Label LSE is pushed onto the
resulting packet. resulting packet.
o The TTL field of the GAL LSE MUST be set to at least 1. The exact o The TTL field of the GAL LSE MUST be set to at least 1. The exact
value of the TTL is application specific. See Section 4.2.1 for value of the TTL is application specific. See Section 4.2.1 for
skipping to change at page 12, line 8 skipping to change at page 12, line 8
o The setting of the TC field of the GAL is application specific. o The setting of the TC field of the GAL is application specific.
See Section 4.2.1 for definition and processing rules. See Section 4.2.1 for definition and processing rules.
LSRs MUST NOT modify the G-ACh message, the ACH or the GAL towards LSRs MUST NOT modify the G-ACh message, the ACH or the GAL towards
the targeted destination. the targeted destination.
Note: This is because once a G-ACh packet has been sent on an LSP, Note: This is because once a G-ACh packet has been sent on an LSP,
no node has visibility of it unless the LSP label TTL expires or no node has visibility of it unless the LSP label TTL expires or
the GAL is exposed when the LSP label is popped. If this is at the GAL is exposed when the LSP label is popped. If this is at
the targeted destination, for example indicated by an address in the targeted destination, for example, indicated by an address in
an ACH TLV, then processing can proceed as specified below. If an ACH TLV, then processing can proceed as specified below. If
this is not the targeted destination, but the node has agreed to this is not the targeted destination, but the node has agreed to
process packets on that ACH channel, then the processing applied process packets on that ACH channel, then the processing applied
to the packet is out of scope of this document. to the packet is out of scope of this document.
Upon reception of the labeled packet, the targeted destination, after Upon reception of the labeled packet, the targeted destination, after
having checked both the LSP Label and GAL LSEs fields, SHOULD pass having checked both the LSP Label and GAL LSEs fields, SHOULD pass
the whole packet to the appropriate processing entity. the whole packet to the appropriate processing entity.
4.2.1.2. MPLS Section 4.2.1.2. MPLS Section
The following figure (Figure 7) depicts an example of an MPLS The following figure (Figure 7) depicts an example of an MPLS
Section. Section.
+---+ +---+ +---+ +---+
| A |-------------| Z | | A |-------------| Z |
+---+ +---+ +---+ +---+
Figure 7: Maintenance over an MPLS Section Figure 7: Maintenance over an MPLS Section
With regard to the MPLS Section, a G-ACh exists between A and Z. Only With regard to the MPLS Section, a G-ACh exists between A and Z.
A and Z can insert, extract or process packets on this G-ACh. Only A and Z can insert, extract, or process packets on this G-ACh.
The following figure (Figure 8) depicts the format of a G-ACh packet The following figure (Figure 8) depicts the format of a G-ACh packet
when used for an MPLS Section. The GAL MAY provide the exception when used for an MPLS Section. The GAL MAY provide the exception
mechanism for a control channel in its own right without being mechanism for a control channel in its own right without being
associated with a specific LSP, thus providing maintenance related associated with a specific LSP, thus providing maintenance-related
communications across a specific link interconnecting two LSRs. In communications across a specific link interconnecting two LSRs. In
this case, the GAL is the only label in the stack. this case, the GAL is the only label in the stack.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GAL | TC |S| TTL | | GAL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ACH | | ACH |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 13, line 23 skipping to change at page 13, line 23
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~ | ~
~ Zero or more ACH TLVs ~ ~ Zero or more ACH TLVs ~
~ (if present) | ~ (if present) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ~ | ~
~ G-ACh message ~ ~ G-ACh message ~
~ | ~ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: G-ACh packet format for an MPLS Section Figure 8: G-ACh Packet Format for an MPLS Section
To send a G-ACh message on a control channel associated to the To send a G-ACh message on a control channel associated to the
Section, the head-end LSR (A) of the Section generates a G-ACh Section, the head-end LSR (A) of the Section generates a G-ACh
message, to which it MAY prepend an ACH TLV Header and appropriate message, to which it MAY prepend an ACH TLV Header and appropriate
ACH TLVs. Next the LSR adds an ACH. Finally it pushes a GAL LSE. ACH TLVs. Next, the LSR adds an ACH. Finally, it pushes a GAL LSE.
o The TTL field of the GAL MUST be set to at least 1. The exact o The TTL field of the GAL MUST be set to at least 1. The exact
value of the TTL is application specific. See Section 4.2.1 for value of the TTL is application specific. See Section 4.2.1 for
definition and processing rules. definition and processing rules.
o The S bit of the GAL MUST be set according to its position in the o The S bit of the GAL MUST be set according to its position in the
label stack. (see Section 4.2). label stack. (see Section 4.2).
o The setting of the TC field of the GAL is application specific. o The setting of the TC field of the GAL is application specific.
See Section 4.2.1 for definition and processing rules. See Section 4.2.1 for definition and processing rules.
Intermediate nodes of the MPLSsection MUST NOT modify the G-ACh Intermediate nodes of the MPLS Section MUST NOT modify the G-ACh
message, the ACH and the GAL towards the tail-end LSR (Z). Upon message, the ACH and the GAL towards the tail-end LSR (Z). Upon
reception of the G-ACh packet, the tail-end LSR (Z), after having reception of the G-ACh packet, the tail-end LSR (Z), after having
checked the GAL LSE fields, SHOULD pass the whole packet to the checked the GAL LSE fields, SHOULD pass the whole packet to the
appropriate processing entity. appropriate processing entity.
4.3. Relationship with RFC 3429 4.3. Relationship with RFC 3429
RFC 3429 [18] describes the assignment of one of the reserved label RFC 3429 [RFC3429] describes the assignment of one of the reserved
values, defined in RFC 3032 [5], to the 'OAM Alert Label' that is label values, defined in RFC 3032 [RFC3032], to the "OAM Alert Label"
used by user-plane MPLS OAM functions for the identification of MPLS that is used by user-plane MPLS OAM functions for the identification
OAM packets. The value of 14 is used for that purpose. of MPLS OAM packets. The value of 14 is used for that purpose.
Both this document and RFC 3429 [18] therefore describe the Both this document and RFC 3429 [RFC3429] therefore describe the
assignment of reserved label values for similar purposes. The assignment of reserved label values for similar purposes. The
rationale for the assignment of a new reserved label can be rationale for the assignment of a new reserved label can be
summarized as follows: summarized as follows:
o Unlike the mechanisms described and referenced in RFC 3429 [18], o Unlike the mechanisms described and referenced in RFC 3429
G-ACh messages will not reside immediately after the GAL but [RFC3429], G-ACh messages will not reside immediately after the
instead behind the ACH, which itself resides after the bottom of GAL but instead behind the ACH, which itself resides after the
the label stack. bottom of the label stack.
o The set of maintenance functions potentially operated in the o The set of maintenance functions potentially operated in the
context of the G-ACh is wider than the set of OAM functions context of the G-ACh is wider than the set of OAM functions
referenced in RFC 3429 [18]. referenced in RFC 3429 [RFC3429].
o It has been reported that there are existing implementations and o It has been reported that there are existing implementations and
running deployments using the 'OAM Alert Label' as described in running deployments using the "OAM Alert Label" as described in
RFC 3429 [18]. It is therefore not possible to modify the 'OAM RFC 3429 [RFC3429]. It is therefore not possible to modify the
Alert Label' allocation, purpose or usage. Nevertheless, it is "OAM Alert Label" allocation, purpose, or usage. Nevertheless, it
RECOMMENDED that no further OAM extensions based on 'OAM Alert is RECOMMENDED that no further OAM extensions based on "OAM Alert
Label' (Label 14) usage be specified or developed. Label" (Label 14) usage be specified or developed.
5. Compatibility 5. Compatibility
Procedures for handling a packet received with an invalid incoming Procedures for handling a packet received with an invalid incoming
label are specified in RFC 3031[8]. label are specified in RFC 3031 [RFC3031].
An LER, LSR or PE MUST discard received associated channel packets on An LER, LSR, or PE MUST discard received associated channel packets
which all of the MPLS or PW labels have been popped if any one of the on which all of the MPLS or PW labels have been popped if any one of
following conditions is true: the following conditions is true:
o It is not capable of processing packets on the Channel Type o It is not capable of processing packets on the Channel Type
indicated by the ACH of the received packet. indicated by the ACH of the received packet.
o It has not, through means outside the scope of this document, o It has not, through means outside the scope of this document,
indicated to the sending LSR, LER or PE that it will process indicated to the sending LSR, LER, or PE that it will process
associated channel packets on the Channel Type indicated by the associated channel packets on the Channel Type indicated by the
ACH of the received packet. ACH of the received packet.
o The packet is received on an Experimental Channel Type that is o The packet is received on an Experimental Channel Type that is
locally disabled. locally disabled.
o If the ACH was indicated by the presence of a GAL, and the first o If the ACH was indicated by the presence of a GAL, and the first
nibble of the ACH of the received packet is not 0001b. nibble of the ACH of the received packet is not 0001b.
o The ACH version is not recognized. o The ACH version is not recognized.
In addition, the LER, LSR or PE MAY increment an error counter and In addition, the LER, LSR, or PE MAY increment an error counter and
MAY also issue a system and/or SNMP notification. MAY also issue a system and/or Simple Network Management Protocol
(SNMP) notification.
6. Congestion Considerations 6. Congestion Considerations
The congestion considerations detailed in RFC 5085 [1] apply. The congestion considerations detailed in RFC 5085 [RFC5085] apply.
7. Major Contributing Authors 7. Major Contributing Authors
The editors would like to thank George Swallow, David Ward, and Rahul The editors would like to thank George Swallow, David Ward, and Rahul
Aggarwal, who made a major contribution to the developement of this Aggarwal who made a major contribution to the development of this
document. document.
George Swallow
Cisco Systems
Email: swallow@cisco.com
David Ward
Cisco Systems
Email: dward@cisco.com
Rahul Aggarwal
Juniper Networks
Email: rahul@juniper.net
8. Acknowledgments 8. Acknowledgments
The editors gratefully acknowledge the contributions of Sami Boutros, The editors gratefully acknowledge the contributions of Sami Boutros,
Italo Busi, Marc Lasserre, Lieven Levrau and Siva Sivabalan. Italo Busi, Marc Lasserre, Lieven Levrau, and Siva Sivabalan.
The authors would also like to thank Malcolm Betts, ITU-T Study Group The authors would also like to thank Malcolm Betts, ITU-T Study Group
15, and all members of the teams (the Joint Working Team, the MPLS 15, and all members of the teams (the Joint Working Team, the MPLS
Interoperability Design Team in IETF and the MPLS-TP Ad-Hoc Team in Interoperability Design Team in IETF and the MPLS-TP Ad Hoc Team in
ITU-T) involved in the definition and specification of the MPLS ITU-T) involved in the definition and specification of the MPLS
Transport Profile. Transport Profile.
9. Security Considerations 9. Security Considerations
The security considerations for the associated control channel are The security considerations for the associated control channel are
described in RFC 4385 [2]. Further security considerations MUST be described in RFC 4385 [RFC4385]. Further security considerations
described in the relevant associated channel type specification. MUST be described in the relevant associated channel type
specification.
RFC 5085 [1] provides data plane related security considerations. RFC 5085 [RFC5085] provides data plane related security
These also apply to a G-ACh, whether the alert mechanism uses a GAL considerations. These also apply to a G-ACh, whether the alert
or only an ACH. mechanism uses a GAL or only an ACH.
10. IANA Considerations 10. IANA Considerations
This document requests that IANA allocates a label value, to the GAL, IANA allocated label value 13 to the GAL from the pool of reserved
from the pool of reserved labels in the "Multiprotocol Label labels in the "Multiprotocol Label Switching Architecture (MPLS)
Switching Architecture (MPLS) Label Values" registry, and suggests Label Values" registry.
this value to be 13.
Note to RFC Editor: The above text "and suggests this value to be
13" needs to be replaced with "with a value of 13." when the RFC
is published and IANA has allocated the value.
Channel Types for the Associated Channel Header are allocated from Channel Types for the Associated Channel Header are allocated from
the IANA "PW Associated Channel Type" registry [4]. The PW the IANA "PW Associated Channel Type" registry [RFC4446]. The PW
Associated Channel Type registry is currently allocated based on the Associated Channel Type registry is currently allocated based on the
IETF consensus process (termed "IETF Review" in [9]). This IETF consensus process (termed "IETF Review" in [RFC5226]). This
allocation process was chosen based on the consensus reached in the allocation process was chosen based on the consensus reached in the
PWE3 working group that pseudowire associated channel mechanisms PWE3 working group that pseudowire associated channel mechanisms
should be reviewed by the IETF and only those that are consistent should be reviewed by the IETF and only those that are consistent
with the PWE3 architecture and requirements should be allocated a with the PWE3 architecture and requirements should be allocated a
code point. code point.
However, a requirement has emerged (see [15]) to allow for However, a requirement has emerged (see [OAM-REQ]) to allow for
optimizations or extensions to OAM and other control protocols optimizations or extensions to OAM and other control protocols
running in an associated channel to be experimented without resorting running in an associated channel to be experimented without resorting
to the IETF standards process, by supporting experimental code to the IETF standards process, by supporting experimental code
points. This would prevent code points used for such functions from points. This would prevent code points used for such functions from
being used from the range allocated through the IETF standards and being used from the range allocated through the IETF standards and
thus protects an installed base of equipment from potential thus protects an installed base of equipment from potential
inadvertent overloading of code points. In order to support this inadvertent overloading of code points. In order to support this
requirement, this document requests that the code point allocation requirement, IANA has changed the code point allocation scheme for
scheme for the PW Associated Channel Type be changed as follows: the PW Associated Channel Type be changed as follows:
0 - 32751 : IETF Review 0 - 32751 : IETF Review
32760 - 32767 : Experimental 32760 - 32767 : Experimental
Code points in the experimental range MUST be used according to the Code points in the experimental range MUST be used according to the
guidelines of RFC 3692 [10]. Functions using experimental G-ACh code guidelines of RFC 3692 [RFC3692]. Functions using experimental G-ACh
points MUST be disabled by default. The Channel Type value used for code points MUST be disabled by default. The Channel Type value used
a given experimental OAM function MUST be configurable, and care MUST for a given experimental OAM function MUST be configurable, and care
be taken to ensure that different OAM functions that are not inter- MUST be taken to ensure that different OAM functions that are not
operable are configured to use different Channel Type values. inter-operable are configured to use different Channel Type values.
The PW Associated Channel Type registry needs to be updated to The PW Associated Channel Type registry has been updated to include a
include a column indicating whether the ACH is followed by a ACH TLV column indicating whether the ACH is followed by a ACH TLV header
header (Yes/No). There are two ACH Channel Type code-points (Yes/No). There are two ACH Channel Type code-points currently
currently assigned and in both cases no ACH TLV header is used. Thus assigned and in both cases no ACH TLV header is used. Thus, the new
the new format of the PW Channel Type registry is: format of the PW Channel Type registry is:
Registry: Registry:
Value Description TLV Follows Reference Value Description TLV Follows Reference
----- ---------------------------- ----------- --------- ----- ---------------------------- ----------- ---------
0x21 ACH carries an IPv4 packet No [RFC4385] 0x21 ACH carries an IPv4 packet No [RFC4385]
0x57 ACH carries an IPv6 packet No [RFC4385] 0x57 ACH carries an IPv6 packet No [RFC4385]
Figure 9: PW Channel Type registry Figure 9: PW Channel Type Registry
IANA is requested create a new registry called the Associated Channel IANA created a new registry called the Associated Channel Header TLV
Header TLV Registry. The allocation policy for this registry is IETF Registry. The allocation policy for this registry is IETF review.
review. This registry MUST record the following information. There This registry MUST record the following information. There are no
are no initial entries. initial entries.
Name Type Length Description Reference Name Type Length Description Reference
(octets) (octets)
Figure 10: ACH TLV registry Figure 10: ACH TLV Registry
11. References 11. References
11.1. Normative References 11.1. Normative References
[1] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Connectivity Verification (VCCV): A Control Channel for Requirement Levels", BCP 14, RFC 2119, March 1997.
Pseudowires", RFC 5085, December 2007.
[2] Bryant, S., Swallow, G., Martini, L., and D. McPherson, [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use Label Switching Architecture", RFC 3031, January 2001.
over an MPLS PSN", RFC 4385, February 2006.
[3] Bradner, S., "Key words for use in RFCs to Indicate Requirement [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Levels", BCP 14, RFC 2119, March 1997. Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
[4] Martini, L., "IANA Allocations for Pseudowire Edge to Edge [RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing
Emulation (PWE3)", BCP 116, RFC 4446, April 2006. in Multi-Protocol Label Switching (MPLS) Networks",
RFC 3443, January 2003.
[5] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers
D., Li, T., and A. Conta, "MPLS Label Stack Encoding", Considered Useful", BCP 82, RFC 3692, January 2004.
RFC 3032, January 2001.
[6] Andersson, L. and R. Asati, "Multiprotocol Label Switching [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word
Class" Field", RFC 5462, February 2009. for Use over an MPLS PSN", RFC 4385, February 2006.
[7] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing in [RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to
Multi-Protocol Label Switching (MPLS) Networks", RFC 3443, Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
January 2003.
[8] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label [RFC5085] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Switching Architecture", RFC 3031, January 2001. Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
[9] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[10] Narten, T., "Assigning Experimental and Testing Numbers [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label
Considered Useful", BCP 82, RFC 3692, January 2004. Switching (MPLS) Label Stack Entry: "EXP" Field Renamed
to "Traffic Class" Field", RFC 5462, February 2009.
11.2. Informative References 11.2. Informative References
[11] Bocci, M., Bryant, S., and L. Levrau, "A Framework for MPLS in [BFD-MPLS] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
Transport Networks", draft-ietf-mpls-tp-framework-00 (work in "BFD For MPLS LSPs", Work in Progress, June 2008.
progress), November 2008.
[12] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "BFD [BFD-VCCV] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding
For MPLS LSPs", draft-ietf-bfd-mpls-07 (work in progress), Detection (BFD) for the Pseudowire Virtual Circuit
June 2008. Connectivity Verification (VCCV)", Work in Progress,
May 2009.
[13] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label [G805] International Telecommunication Union, "Generic
Switched (MPLS) Data Plane Failures", RFC 4379, February 2006. Functional Architecture of Transport Networks", ITU-
T G.805, March 2000.
[14] Nadeau, T. and C. Pignataro, "Bidirectional Forwarding [MPLS-TP] Bocci, M., Bryant, S., and L. Levrau, "A Framework for
Detection (BFD) for the Pseudowire Virtual Circuit MPLS in Transport Networks", Work in Progress,
Connectivity Verification (VCCV)", draft-ietf-pwe3-vccv-bfd-04 November 2008.
(work in progress), May 2009.
[15] Vigoureux, M., Ward, D., and M. Betts, "Requirements for OAM in [OAM-REQ] Vigoureux, M., Ed., Ward, D., Ed., and M. Betts, Ed.,
MPLS Transport Networks", "Requirements for OAM in MPLS Transport Networks", Work
draft-ietf-mpls-tp-oam-requirements-01 (work in progress), in Progress, March 2009.
March 2009.
[16] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and [RFC3429] Ohta, H., "Assignment of the 'OAM Alert Label' for
S. Ueno, "MPLS-TP Requirements", Multiprotocol Label Switching Architecture (MPLS)
draft-ietf-mpls-tp-requirements-08 (work in progress), Operation and Maintenance (OAM) Functions", RFC 3429,
May 2009. November 2002.
[17] International Telecommunication Union, "Generic Functional [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Architecture of Transport Networks", ITU-T G.805, March 2000. Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[18] Ohta, H., "Assignment of the 'OAM Alert Label' for [TP-REQ] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M.,
Multiprotocol Label Switching Architecture (MPLS) Operation and Ed., Sprecher, N., and S. Ueno, "MPLS-TP Requirements",
Maintenance (OAM) Functions", RFC 3429, November 2002. Work in Progress, May 2009.
Authors' Addresses Authors' Addresses
Matthew Bocci (editor) Matthew Bocci (editor)
Alcatel-Lucent Alcatel-Lucent
Voyager Place, Shoppenhangers Road Voyager Place, Shoppenhangers Road
Maidenhead, Berks SL6 2PJ Maidenhead, Berks SL6 2PJ
UK UK
Email: matthew.bocci@alcatel-lucent.com EMail: matthew.bocci@alcatel-lucent.com
Martin Vigoureux (editor) Martin Vigoureux (editor)
Alcatel-Lucent Alcatel-Lucent
Route de Villejust Route de Villejust
Nozay, 91620 Nozay, 91620
France France
Email: martin.vigoureux@alcatel-lucent.com EMail: martin.vigoureux@alcatel-lucent.com
Stewart Bryant
Cisco
Email: stbryant@cisco.com
George Swallow
Cisco
Email: swallow@cisco.com
David Ward
Cisco
Email: dward@cisco.com
Rahul Aggarwal Stewart Bryant (editor)
Juniper Networks Cisco Systems
Email: rahul@juniper.net EMail: stbryant@cisco.com
 End of changes. 104 change blocks. 
277 lines changed or deleted 253 lines changed or added

This html diff was produced by rfcdiff 1.35. The latest version is available from http://tools.ietf.org/tools/rfcdiff/